Reducing the effect of cyanobacteria in the microfiltration of secondary effluent

Abstract

Cyanobacterial blooms in the lagoons of sewage treatment plants can severely impact the performance of membrane plants treating the effluent. This paper investigates the impact of Microcystis aeruginosa in a secondary effluent on the microfiltration filterability and cleaning of the membrane. Alum coagulation and dissolved air flotation (DAF) were investigated to remove the algae and so enhance the volume of effluent processed, and their influence on reversible and irreversible fouling. Degree of fouling due to the algal components was found to be in decreasing order of algal cells, algal organic matter and extracellular organic matter. Alum coagulation with 5 mg L⁻¹ as Al³(+) led to a substantial increase in permeate volume, an increase in dissolved organic carbon removal, and a foulant layer which protected the membrane from internal fouling but which was hydraulically removable resulting in full flux recovery. Pre-treatment by DAF or 1.5 μm filtration following alum coagulation enhanced the flux rate and permeate volume but exposed the membrane to internal irreversible fouling.

Effect of feedwater pre-treatment using UV/H 2 O 2 for mitigating the fouling of a ceramic MF membrane caused by soluble algal organic matter

“…AOM has been demonstrated to cause severe fouling for low-pressure polymeric [5][6][7][8] and ceramic membranes [9,10] as it contains a high proportion of high molecular weight (MW) biopolymers such as polysaccharides and proteinaceous substances which have been identified as the most problematic foulants for the membranes. Moreover, the blooms can lead to the release of harmful algal metabolites including toxins into the drinking water, posing a threat to human health [11].…”

Treatment of secondary effluent with biological activated carbon to reduce fouling of microfiltration membranes caused by algal organic matter from Microcystis aeruginosa

“…AOM comprises mainly high molecular weight (MW) organics such as protein-like and polysaccharide-like substances [5] which can cause severe membrane fouling and lead to decrease in membrane permeability [3,4]. It has been demonstrated that the presence of AOM in addition to the effluent organic matter in secondary effluent can further reduce the efficiency of LPM filtration [6,7], thus increasing the operating cost. However, Lee and Walker [8] reported that hydrophobic polysulfone UF membrane could remove 91% of microcystin-LR whereas hydrophilic CA membranes adsorbed little or no microcystin-LR.…”

“…Studies show that the fouling potential of the AOM from M. aeruginosa is greatest at the stationary phase of growth [4,6,9]. Goh et al [6] reported that the extracellular organic matter caused greater fouling than the cells during stationary phase.…”

“…Goh et al [6] reported that the extracellular organic matter caused greater fouling than the cells during stationary phase. Studies have shown that proteins in secondary effluent were responsible for the irreversible fouling of UF and MF membranes [10,11].…”

“…Goh et al [6] demonstrated that coagulation could improve polymeric membrane MF of secondary effluent containing AOM derived from M. aeruginosa. Zhang et al [18] investigated the effect of different coagulants (aluminium-and iron-based) for reducing AOM fouling of a ceramic MF membrane and found that aluminium chlorohydrate was the most cost effective coagulant for minimising irreversible fouling.…”